1. Field of the Invention
The present invention pertains to pipe connector apparatus and methods for installing the same. More specifically, it pertains to apparatus and methods suitable for connecting pipes in particularly difficult environments, such as subsea ones. In particular, the present invention pertains to connector apparatus for repairing damaged pipe risers at offshore oil and/or gas platforms.
2. Description of the Prior Art
In offshore production of oil and/or gas, subsea pipelines are commonly connected to production equipment or piping manifolds located above the surface of the water on a platform. A normal way of making such connection is through a vertical section of pipe, commonly referred to as a "riser". Frequently, the riser is damaged through corrosion, collision with ocean-going vessels, etc. The riser is most commonly damaged in the "splash zone" area near and just below the surface of the water.
The task of repairing a damaged riser, particularly one which is damaged below the surface of the water, is not a simple one. Such repairs have been commonly done by welding. However, welding techniques now employed require large amounts of labor and equipment.
In recent years, hydraulic couplings have been used to connect sections of pipe. However, such couplings require a source of pressurized hydraulic fluid and requires some means of maintaining engagement of the coupling with the pipe when the fluid pressure is relieved. For example, one coupling of the prior art utilizes epoxy resin as its fluid, allowing the resin to set in order to hold the coupling in its engaged position. Such setting procedures are complex and not totally reliable. Neither do they allow subsequent tightening of seals or easy removal of the coupling for repair or replacement. An example of such a coupling is shown in U.S. Pat. No. 3,393,926. Furthermore, such couplings have been normally designed for both tension and compression forces present in most pipeline situations, and are relatively complex for a riser installation where large reverse stresses are not prevalent.
Later couplings, such as the one shown in U.S. Pat. No. 3,999,782, have been developed to eliminate the problems inherent with hydraulically actuated couplings. Such couplings utilize totally mechanical means of actuation, eliminating much of the manpower and equipment required for other coupling means. However, such couplings have been primarily designed for both tension and compression forces and are relatively complex for repair of a damaged riser.